This invention relates to an improved silver halide display element. More specifically, it relates to such a display element comprising at least five separately sensitized light-sensitive silver halide emulsion layers containing, in addition to the three conventional cyan, magenta, and yellow dye-forming layers, a fourth image dye-forming layer comprising a coupler wherein the dye formed by that coupler has a CIELAB hab hue angle in the range of from not less than 355xc2x0 to not more than 75xc2x0, and a fifth image dye-forming layer comprising a coupler wherein the dye formed by that coupler has a hue angle in the range of from not less than 225xc2x0 to not more than 310xc2x0, which increases the gamut of colors possible.
It is known in the art that photographic display materials are utilized for advertising, as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters, and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness, and flatness. Cost is also important, as display materials tend to be expensive compared with alternative display material technology, mainly lithographic images on paper. For display materials, traditional color paper is undesirable, as it suffers from a lack of durability for the handling, photoprocessing, and display of large format images.
Prior art silver halide display materials typically utilize yellow, magenta, and cyan dyes to create an image. In a typical yellow, magenta, and cyan imaging system the color gamut is limited compared to printing of color inks. Color gamut is an important feature of color printing and imaging systems. It is a measure of the range of colors that can be produced using a given combination of colorants. It is desirable for the color gamut to be as large as possible. The color gamut of the imaging system is controlled primarily by the absorption characteristics of the set of colorants used to produce the image. Silver halide imaging systems typically employ three colorants, typically including cyan, magenta, and yellow in the conventional subtractive imaging system.
The ability to produce an image containing any particular color is limited by the color gamut of the system and materials used to produce the image. Thus, the range of colors available for image reproduction is limited by the color gamut that the system and materials can produce.
Color gamut is often thought to be maximized by the use of so-called xe2x80x9cblock dyesxe2x80x9d. In The Reproduction of Colour 4th ed., R. W. G. Hunt, pp 135-144, it has been suggested that the optimum gamut could be obtained with a subtractive three-color system using three theoretical block dyes where the blocks are separated at approximately 490 nm and 580 nm. This proposal is interesting but cannot be implemented for various reasons. In particular, there are no real organic based couplers which produce dyes corresponding to the proposed block dyes.
Variations in the block dye concept are advanced by Clarkson, M. E. and Vickerstaff, T. in xe2x80x9cBrightness and Hue of Present-Day Dyes in Relation to Colour Photography,xe2x80x9d Photo. J. 88b, 26 (1948). Three example spectral shapes are given by Clarkson and Vickerstaff: Block, Trapezoidal, and Triangular. The authors conclude, contrary to the teachings of Hunt, that trapezoidal absorption spectra may be preferred to a vertical sided block dye. Again, dyes having these trapezoidal spectra shapes are theoretical and are not available in practice.
Both commercially available dyes and theoretical dyes were investigated in xe2x80x9cThe Color Gamut Obtainable by the Combination of Subtractive Color Dyes. Optimum Absorption Bands as Defined by Nonlinear Optimization Technique,xe2x80x9d J. Imaging Science, 30, 9-12. The author, N. Ohta, deals with the subject of real colorants and notes that the existing curve for a typical cyan dye, as shown in the publication, is the optimum absorption curve for cyan dyes from a gamut standpoint.
Bourdelais et al in U.S. Pat. No. 6,030,756 discusses imaging layers containing silver halide and dye forming couplers applied to both sides of a translucent base for a display material. While the display material in U.S. Pat. No. 6,030,756 provides an excellent image that can be displayed without the need for a backlight source, the image is only capable of reproducing 56% of Pantone color space.
McInerney et al in U.S. Pat. Nos. 5,679,139; 5,679,140; 5,679,141; and 5,679,142 teach the shape of preferred subtractive dye absorption shapes for use in four color, C,M,Y,K based ink jet prints.
McInerney et al in EP 0 825 488 teaches the shape of preferred subtractive cyan dye absorption shape for use in silver halide based color prints.
Kitchin et al in U.S. Pat. No. 4,705,745 teaches the preparation of a photographic element for preparing half-tone color proofs comprising four separate imaging layers capable of producing cyan, magenta, yellow, and black images.
Powers et al in U.S. Pat. No. 4,816,378, teaches an imaging process for the preparation of color half-tone images that contain cyan, magenta, yellow, and black images. The use of the black dye does little to improve the gamut of color reproduction.
Haraga et al in EP 0 915 374 A1 teaches a method for improving image clarity by mixing xe2x80x98invisiblexe2x80x99 information in the original scene with a color print and reproducing it as an infrared dye, magenta dye, or as a mixture of cyan, magenta, and yellow dyes to achieve improved color tone and realism. The addition of the resulting infrared, magenta, or black dye does little to improve the gamut.
In spite of the foregoing teachings relative to color gamut, the coupler sets which have been employed in silver halide color imaging have not provided the range of gamut desired for modem digital imaging; especially for so-called xe2x80x98spot colorsxe2x80x99, or xe2x80x98HiFi colorsxe2x80x99.
It is, therefore, a problem to be solved by providing a coupler set which provides an increase in color gamut compared to coupler sets comprised of cyan, magenta, and yellow dye forming couplers by further incorporating red dye and blue dye forming couplers.
It has been proposed in U.S. Pat. No. 5,866,282 (Bourdelais et al) to utilize a composite support material with laminated biaxially oriented polyolefin sheets as a photographic imaging material. In U.S. Pat. No. 5,866,282, biaxially oriented polyolefin sheets are extrusion laminated to cellulose paper to create a support for silver halide imaging layers. The biaxially oriented sheets described in U.S. Pat. No. 5,866,282 have a microvoided layer in combination with coextruded layers that contain white pigments such as TiO2 above and below the microvoided layer. In the composite imaging support structure described in U.S. Pat. No. 5,866,282 the silver halide imaging layers are applied to the white, reflecting side of the base that has a spectral transmission less than 15%.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin coated clear polyester sheet. Incorporated diffusers are necessary to diffuse the light source used to backlight transmission display materials. Without a diffuser, the light source would reduce the quality of the image. Typically, white pigments are coated in the bottommost layer of the imaging layers. Since light sensitive silver halide emulsions tend to be yellow because of the gelatin used as a binder for photographic emulsions, minimum density areas of a developed image will tend to appear yellow. A yellow white reduces the commercial value of a transmission display material because the imaging viewing public associates image quality with a white white. It would be desirable if a transmission display material with an incorporated diffuser could have a more blue white since a white that is slightly blue is perceptually preferred as the whitest white.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin subbed clear polyester sheet. TiO2 is added to the bottommost layer of the imaging layers to diffuse light so well that individual elements of the illuminating bulbs utilized are not visible to the observer of the displayed image. However, coating TiO2 in the imaging layer causes manufacturing problems such as increased coating coverage which requires more coating machine drying and a reduction in coating machine productivity as the TiO2 requires additional cleaning of coating machine. Further, as higher amounts of TiO2 are used to diffuse high intensity backlighting systems, the TiO2 coated in the bottommost imaging layer causes unacceptable light scattering reducing the quality of the transmission image. It would be desirable to eliminate the TiO2 from the image layers while providing the necessary transmission properties and image quality properties.
It has been proposed in U.S. Pat. No. 6,017,685 (Bourdelais et al.) to utilize biaxially oriented polyolefin microvoided sheet laminated to polyester for a display base. In U.S. Pat. No. 6,017,685 the incorporated voided layer diffuses the illumination light source avoiding the problems with incorporated TiO2 as a diffuser screen. Disclosed in U.S. Pat. No. 6,017,685 are yellow, magenta, and cyan dyes formed by silver halide process and, thus, the silver halide image disclosed in U.S. Pat. No. 6,017,685 has a limited dye gamut compared to printed inks.
There is a need for a display imaging material that provides an expanded color gamut while maintaining processing efficiency.
It is an object of the invention to provide improved imaging layers.
It is another object to provide imaging material that has an expanded color gamut.
It is a further object to maintain processing efficiency of the slver halide image.
It is a another object to provide more efficient use of the light used to illuminate transmission display materials.
These and other objects of the invention are accomplished by an imaging element comprising a transparent polymer sheet, and at least one photosensitive dye forming coupler containing layer is on each side of said transparent sheet, wherein there are at least four separate photosensitive layers and the photosensitive layers comprise at least four dye forming couplers that form at least four spectrally distinct colors, and wherein said imaging element is adhered to a transmissive polymer sheet that has a spectral transmissiveness of greater than 15 and less than 90%.
The invention provides a display imaging material with an improved color gamut while maintaining typical the 45 second color development time.